I'm watching a fascinating video on bloggingheads.tv in which Sean Carroll of Cosmic Variance and John Horgan talk about modern comsology. An interesting point from my point of view is that the basic reason modern cosmology exists is because the idea of maximum likelihood doesn't seem to apply to the universe -- probabilistically the universe "shouldn't be" like it is. But it is! From an epistemological point of view that's why explaining the way the universe is is interesting -- you don't expect, for example, large-scale homogeneity and isotropy, but it's there!
(Also, bloggingheads has a feature by which you can speed up videos by a factor of 1.4, without the expected raise in pitch of the sound by a tritone. This is nice, because when listening to recorded speech I often find it to be too slow. That's fine -- I don't insist that people should speak faster -- but I can take in information faster than an extemporaneous speaker can produce it.)
Nothing particularly new if you know something about these things, but a good way to spend 47 (sped-up) or 66 (normal-speed) minutes on a Saturday afternoon.
Showing posts with label cosmology. Show all posts
Showing posts with label cosmology. Show all posts
15 March 2008
14 January 2008
Am I a naked brain?
Guess what, folks? Probability and cosmology are weird when they interact. (Big Brain Theory: Have Cosmologists Lost Theirs?, by Dennis Overbye, January 15, 2008 NY Times.)
Basically, it appears to be more likely that we are some sort of naked brain living in an illusion of a world than that we live in the actual world we perceive. Roughly speaking, this occurs if we assume that the universe is infinite -- and thus everything that can occur does occur -- because a naked brain is supposedly much more likely to form by chance than the reality we think surrounds us does.
The obvious rebuttal, if one is wedded to this particular model of cosmology, is an evolutionary one -- maybe naked brains aren't so likely after all, because brains are produced (or so we think) by evolutionary processes, so is one really so likely to find a brain just sitting there without the biology in which it evolved? Overbye's article only mentions physicists; I wonder what (if anything) the biologists have to say. And I don't think our probabilistic understanding of evolution is quite to the point where the first sentence of this paragraph can be made rigorous. (On this point, I'd love to be told I'm wrong!)
edit: Sean at Cosmic Variance has written about this much more insightfully than I, and with links to a lot of the relevant research.
Basically, it appears to be more likely that we are some sort of naked brain living in an illusion of a world than that we live in the actual world we perceive. Roughly speaking, this occurs if we assume that the universe is infinite -- and thus everything that can occur does occur -- because a naked brain is supposedly much more likely to form by chance than the reality we think surrounds us does.
The obvious rebuttal, if one is wedded to this particular model of cosmology, is an evolutionary one -- maybe naked brains aren't so likely after all, because brains are produced (or so we think) by evolutionary processes, so is one really so likely to find a brain just sitting there without the biology in which it evolved? Overbye's article only mentions physicists; I wonder what (if anything) the biologists have to say. And I don't think our probabilistic understanding of evolution is quite to the point where the first sentence of this paragraph can be made rigorous. (On this point, I'd love to be told I'm wrong!)
edit: Sean at Cosmic Variance has written about this much more insightfully than I, and with links to a lot of the relevant research.
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